Leveling with Arc can be broken into the following parts.
Up to level 10. It is super worthy. You do it any way you want. Usually you will donate to someone else FP and he will donate back into yours. Both of you will earn the rewards, and this is called FP swap.
Then you need to level the Arc to around level 30. (Though some would say up to 27 may be enough). This is harder then before. You need to put more FP into each level, and you only earn back 1% per level. Again you do it through the FP swaps.
At this magical point everything change. From level 30 (or so) till level 74 something else happens.
Lets take, for example, level 54.
The Arc needs 2875 FP to level.
The first reward is worth 855 FP.
The second reward is worth 430 FP.
The 3rd eward value is 145 FP
Now, instead of doing the general swap with your friend/guild. You talk with me and Moshe. we both got a level 80 Arc, which gives us 91% return on the reward.
I don't need to swap any point with you. I can put half of the 2875 points into the arc, thats 1438 FP's. If I put 1438 FP's I will lock the first reward and no one can steal it from me. WIth my Arc, the first reward of 855, will return to me 855*1.91 = 1633 FP's.
So, you didnt give me even a single FP. I donated the whole 1438 FP to lock the first reward out of my personal packs. But when you level the arc, I will get back 1633 FP's. That means that I just got an extra 195 FP's.
You also talk with Moshe. He do the same to lock the 2nd reward. For that he invest, out of his personal packs, some 719 FPs to lock the 2nd place. When your arc levels, he will get back 821 FP. So moshe earn some 104 FP back.
So far, you didn't put even ONE FP into your Arc. And already your arc is 3/4 of the way to be filled. You need to fill now 820 FP to get it to the next level. You start to fill the Arc with a few hundred FP, till the 3rd reward is worth sniping. To fill those you either put FP yourself, or do some FP swaps with friends/guild.
When 3rd reward is worth sniping, you talk with Rambo and he put 261 points to lock the 3rd spot (thats a 180% over the reward, which is customary).
At the end, instead of filling 2875 points, you need to fill only 560 FP's. Thats like a level 6 Arc. You can easily do it in a day or two, and then again level the next level with the help of me, moshe and rambo.
The reason the Arc start to level really fast after level 30, is that it is very worthy for the high Arc levels to put the FP into your arc (they will earn a lot), and you need to just level a very small part of the level.
If rambo, moshe and me are with you in a guild, we may put more the just the minimal half, as it is custome to put 180% of the reward. I.e. for the first reward, if you were in my guild, I would put 1539 FP's. Moshe will put 774. Between the 3 of us, we will donate to you (free of any charge) some 2574 FP. And you need to fill up the rest of the which is only..... 301 FP!!!!!!!!
Yes, if you going to level an Arc level 54, and you got good friends/guild that do the 1.8 donation, you need to pay only 301 FP to level the Arc to level 55!!!!!!
And that's why those level fly so fast. You pay less to level an Arc level 54 then an Arc level 5!